Method of and apparatus for making casts



Oct. 13, 1936. c, MaCDoNALD 'METHOD OF AND APPARATUS FOR MAKING CASTS Filed May 25, 1933 3 Sheets-Sheet 1 METHOD OF AND APPARATUS FOR MAKING CASTS' s Shets-Sheet 2 Oct. 13, 1936. c. K. MacDONALD Filed May 25, 1955 Oct. 13, 193 K, MaCDONALD 2,057,039

METHOD OF AND APPARATUS FOR MAKING CASTS Filed May 25, 1955 3 Sheets-Sheet 5 33 35 44 k :03 F? 42 a 1 a :z 352w Patented Oct. 13, 1936 UNITED STATES METHOD OF AND APPARATUS FOR MAKING CASTS Clifford K. MacDonald, Brockton, Mass, assignor to United Shoe Machinery Corporation, Paterson, N. J., a corporation of New Jersey Application May 25, 1933, Serial No. 672,861

29 Claims.

This invention relates to methods of making casts and other replicas and to apparatus for use in making such objects and is herein illustrated with reference to the production of plaster casts of human feet.

When making a cast of a particular article it is necessary first toprocure a mold or matrix which will correspond exactly in shape to the article which is to be reproduced. This may be done by placing the article in plastic material such, for example, as plaster of Paris or wax in liquid form, and holding the article stationary in the plastic material while the latter sets. After the plastic material has hardened, the article is removed thereby leaving an impression in the mold which corresponds in shape to the outer surface of the article.

It will be seen that considerable time is lost in making molds in the manner described above because the article must remain in the plastic material until the latter has completely hardened. Moreover, if the mold is, for example, of wax and is to be used only once or twice for a special purpose and thereafter reduced to a plastic condition and used in making a diiferent shaped mold, additional time is lost while the material is being melted or otherwise brought into a plastic condition before it can be used again. 7

When a mold is tobe made from an animate object such as a human foot another difficulty arises. Unless the foot is held perfectly stationary while the plastic material is setting, the resulting impression will not correspond exactly in shape to the outside surface of the foot. It is extremely difficult for a person to hold his foot perfectly still during the time it takes for the available plastic material to set, unless the foot is resting on a support, which, of course, will prevent a perfect impression from being obtained. Moreover, the heat of many plastic materials in melted form, even when not so great as to be prohibitive, makes it even more difficult to secure good results. A further objection to this method of making casts arises from the fact that it is practically impossible to secure an impression of a foot while the latter is supporting the weight of the body because, obviously, the plastic material itself affords no support upon which the person can bear his weight and, as stated, if a support for the foot is used, the resulting impression will not be perfect at those portions of the foot which engage the support.

Objects of the present invention are to provide an improved method of making casts or other replicas whereby difficulties such asthose pointed out above will be eliminated, and toprovide also an improved apparatus for carrying out this method.

The illustrated method in one aspect consists in reproducing an article by making an impression of the article in magnetizable granulated material which is in a mobile condition and, while the article .is still restingin the material, rendering the latter immobile by magnetization so that .the

article maybe removed and the impression used for making a plastencast of the article. As illustrated,'the mobile granulated material comprises a mass of small particles, preferably balls of .mag-

netizable material, for exampleironor steel, which U rest loosely on a support in a container and which are readily displaceable by pressure so that ,they may be molded to the shape of an article pressed against them. The mass of magnetizable particles or balls is rendered immobile by means of a mag-. net, preferably an electro-magnet, which causes a. magneticrfield to pass through the space 007 cupied by the balls and causes the latter tobecome rigid and to remain rigid as long as the magnetic field is maintained, ,An impression thus formed in the mass of magnetizable balls can be used at once as a mold from which to make a plaster cast of the article which was used in making the impression, thereby saving thetime which it would ordinarily take for a mold composed of plastic material such as wax or plaster of Paris to harden. y

In making a cast of a foot by the method of the present invention, the foot is pressed against the magnetizable particles or balls until it sinks to the desired depth and a magnetic field is then set up in the space occupied bythe balls to cause them to become locked rigidly in position, thereby retaining the impression formedtherein so that the foot may be removed at once without injuring the impression. Since the balls afiord a support for the foot, the entire weight: of-the body may be placed thereon if it is desired to obtain an impression of the foot while the latter is supporting the weight of the body. 7

The illustrated apparatus which constitutes a preferred embodiment of theinvention in its apparatus aspect, and which may beused as an aid to the practice of my new method, isprovided with a hollow frame or container, means for supporting a mass of magnetizable particles .or balls within the container, and meansfor setting up a magnetic field in the space occupied by the magnetizable material. The supporting means is illustrated as composed of a non-magnetizable substance and is adjustable so thatthe upper the magnetic'fiux to extend into such portions and set up a magnetic field between them. In

' order to control the mobility of the mass of balls,

means such as a'rheostat is preferably provided for varying the strength of the current sent through the coils of the magnet.

With the above and other objects in view, the invention will now be described with reference to the accompanying drawings and pointed out in the appended claims.

In the drawings, a

Fig. 1 is a side elevation of the apparatus embodying the present invention witha foot mounted therein, the frame or container being shown in section and the magnet being illustrated with its centralportion broken out; V r

YF-ig. 2 is a plan view of theapparatus shown in Fig.1 with the support broken away to illustrate. details, the foot being shown in brokenlines;

Fig. 3 is a cross-sectional view of the apparatus 7 taken on the line IIIIII of Fig. 1-;

Fig. 4 is a view similar to Fig; 1 after an impression of the foot has been made in the iron balls, the impression lined and filled with plastic material, and a spirit level placed in the plastic material at the heel end of the impression;

Fig. 5is a view similar to Fig. 4 after the cast of the foot has been removedfrom the balls and the current of the magnet hasbeen'turned off;

and

' Fig. 6. is aperspe'ctive view of the finished cast.

The apparatus and.method disclosed herein for producing casts are adapted for use in the manufacture of orthopedic shoes and are illustrated herein with reference to the production of casts of feet for which orthopedic shoes are to be made.

It is tobe'understood, however, that in many of its aspects the invention is not limited to the production of casts 'of feetfor orthopedic shoe work but may be employed to advantage in many other instances where exact reproductions of particular articles are required.

The illustrated apparatus comprises an elongated rectangular frame or container I0 which is preferably about 8 or 10 incheshigh and is open at the top and bottom The container has an inside area which is large enough to permit an adult persons foot to be conveniently located therein'and still leave considerable space around the foot. The vertical side walls I2, I4 of the container, as illustrated herein, are formed of relatively thick plates of iron or steel, the outer as their lower surfaces.

surfaces of which taper inwardly at the upper whereby the container may be positionedon-the upper side of a large magnet 20, illustrated herein as an electro magnet. Theends of the rectangular container are formed by a pair of'thin plates [6 and I8, preferably of brass or some other relatively non-magnetizable material, which are 7 secured to the side plates 12 and M by means of screws l9. n

Theelectro-magnet 20 upon which the container rests is a horse-shoeor L l-shaped magnet having soft iron cores 22 and 24 connected by a horizontal yoke piece 26, the cores being secured to the yoke piece by. means of screws 28. The cores 22 and 24 are wound repectively with magnetizing coils 30, 32 of insulated wire through which a current is passed around the cores to magnetize the latter and 'set up a magnetic field having lines of force extending between the cores. The upper ends of the cores 22, 24 have projections or shoulders formed thereon which are located outside the downwardly projecting tainer I0 'can be conveniently located centrally of the electro-magnet. As shown in Fig. 1, the cores and the yoke piece 26 are equal in length to the rectangular container and the cores are substantially uniform in cross section. When the container I0 is mounted on. the electro-magnet, the side walls l2 and l4 form extensions of the poles 22, 24 so that the magnetic flux of the magnet will extend into the side walls and producea relative ly strong magnetic field between such walls. Inorder that the magnetic field between the side walls 12 and 14 will be sufficiently strong, those parts of the apparatus which are located between '22 and 24, which form the poles of the magnet,

the wallsya'nd which would have a tendency to,

reduce the strength or density of the field if they were composed of magnetizable materials, are

made of relatively non-magnetizable materials such as brass or aluminum, as will hereinafter appear, so that the magnetic field will be concentrated as much as possible between the side walls l2 and I4 7 2 'Instead of making the container l0 asa separate unit to be mounted on the electro-magnet20 in the manner described, the soft iron cores 22 and 24 which form the poles of the electro--mag' net may, if desired; be extended upwardly beyond the magnetizing coils 3D, 32 to form the side walls of'the container, the end walls of the container being secured to thesecores in the manner set forth above. With this construction, in which.

the cores of the electro-magnet also form the side walls of the container, there will, of course,

' be no joints or breaks in the opposite poles of the electro-magnet.

The magnetizing coils 3 0, 32 of the electro magnet are wound in'series and a rheostat 34is provided for varying and controlling the strength ofthe current passed through the coils. The rheostat is" indicated diagrammatically in the drawings and is adapted to turn the current on and off, or to permit only a limited amount of current to pass through they coils so that the strength of the magnetic field can be increased or reduced as desired. The electro-magnet 20 and the container I0 mounted thereon form a complete unit which may be mounted, for example, on a base 3| and moved about on wheels or casters, or it may, if desired, be incorporated in part of the present invention it has not been shown in detail.

Mounted inside the rectangular container or frame lflis-a supporting member'35 (Fig. 1) ofaluminum or an aluminum alloy, the member 35 being made up of several sections which are pivotally connected together so that they can be adjusted to different positions heightwise of the container. A forward or toe supporting section 36 o'f the supporting member 35 is fixedly secured by screws 38 and 40 to the sidewalls of the container, the screws passing through downwardly projecting flanges on the section 36 which contact with the inner surfaces of the side walls l2 and I4 so that the upper surface of the section will occupy the full space widthwise of the container. The forward end of the section 36 abuts against the brass plate l6 so that no space is left between the section '36 and the container at the front end thereof. A middle or shank supporting section 42 of the supporting member 35, having its "forward end engaging the rear end of the fixed section 36, is pivotally mounted in the side walls l2 and I4 by means of a pair of cylindrical lugs or trunnions 44, 46 which are formed at each side of the forward end of the section 42 and extend into circular openings formed in the inner portions of the side walls. Assho-wn in Fig. 1, this middle section 42 normally extends rearwardly or toward the heel end of the container on an upward incline, thereby causing the central or intermediate portion of the supporting member 35 to conform more closely to the longitudinal curvature of the shank portion of a foot.

Projecting downwardly from the forward end of the inclined middle section 42 is a pairof ears 48 and pivotally connected to these cars by means of a pin 50 is a'horizontal link 52, which extends rearwardly and is pivotally connected by a bolt 53 to another pair of ears 54 projecting downwardly from the lower side of an upwardly extending supporting arm 56. The arm 56 is pivotally mounted in circular recesses formed in the opposite side walls of the container Ill by means of cylindrical lugs or trunnions 58 and 60 which project horizontally from opposite sides ofthe arm. The upper end of the arm 56 is pivotally secured to a pair of downwardly projecting lugs 6| formed on the under side of a third section 62 of the supporting member 35, the section 62 being pivotally connected at its forward end to the middle section 42 by short horizontal pins 64, 66 fastened to the third section'by set screws and extending through circular openings in apair of small rectangular plates which are retained in lugs in the middle section 42 by two pairs of pins, indicated by the numerals 68 and 10. This arrangement insures that there will be no open space left at the point where the upper surface of the section 62 of the supporting member 35 joins the upper surface of the section 42. The rear end of the section 62 terminates a short distance inside the brass end plate I8 and has an upwardly projecting portion 12 formed thereon which provides a vertical back or end plate for the sectional supporting member 35. The middle section 42 and the rear section 62 are .both substantially as wide as the space between the inner surfaces of theside Walls of the container will permit, having only the clearance necessary to permit adjustment of these sections.

The Manor heel end supporting section 62 is located in a substantially horizontal position, as shown'in Fig. 1, and maybe adjusted heightwise of the container while supported in this position. To effect such adjustment there is provided a horizontal shaft 14 which extends through the lowerportion of "the container I 6 and-atits inner mass of iron balls 90.

end is threaded into a'large lug 16 formed on the forward end of the bolt 53 which connects the horizontallink 52 to the downwardly projecting ears 54 on the supporting arm 56. The middle portion of the shaft 14 is supported in the container by means of a horizontal'bracket I 8 which is' pivotally mounted between the side walls I 2 and M by means of a pair of cylindrical lugs or trunnions 80, 82 which extend into horizontal recesses formed in the side walls. In order to prevent the shaft 14 from moving lengthwise of the container, a pair of collars '84, 86 are pinned to the shaft at either side of the supporting bracket 18, as shown in Fig. 2.

The forward end of the shaft 14 extends through an opening in the brass end plate I 6 and has fixedly mounted thereon a hand wheel 88 by which the shaft may be rotated in its bearings in the bracket 18. By rotating the shaft 14 the lug 16 will be moved along the threaded portion of the shaft to swing the supporting arm 56 about its pivots 58, 60, thereby causing the rear end of the section 62 to be raised or lowered as the case may be. When the arm 56 is rotated the horizontal link 52, which extends between thisarm and the ears 48 of the middle section 42,'will cause the section 42 to: be rotated about its pivots 44, 4'6 and to move an amount equal to the movement of the supporting arm 56. In this way the section 62 is always maintained in a horizontal position regardless of the height to which it is adjusted, and the middle section 42, which pivots about its forward end, will be inclined at different angles depending upon the heightwise position of the horizontal section 62. The above arrangement permits the supporting member 35 to be adjusted until its upper surface assumes a shape which'will conform substantially to the longitudinal curvature or contour of the bottom surface of the foot being operated upon regardless of the shape of such foot.

The aluminum supporting member 35 is adapted to support a mass of mobile magnetizable material which is illustrated herein as a relatively thick layer of small iron or steel balls 90 piled loosely on the upper surface of the supporting member. As shown in Figs. 1 and 3, the balls 30 cover the upper surface of the supporting member with a layer of mobile material which is from about 1 to 2 inches thick. Since the balls rest loosely on the member 35 and are not more than of an inch in diameter, they may be readily pressed into different positions when an object, for example, a human foot is pressed forcibly against them. This loose, mobile condition of the mass of balls permits them to be pressed closely against the surfaces of an object forced against them so that an impression formed in the mass of balls will correspond accurately to the shape of the object. I

In the use of the illustrated apparatus, which may be referred to as a magnetic box, an article to be reproduced, for example, a human foot 92, is placed in the container against the mobile In making a'cast of a foot the proper adjustments should, of course, be made in the sectional support 35 by means of the hand wheel 88 to accommodate the support to the longitudinal contour of thefoot or, in other words, to position the support in accordance with the toe spring and heel height of the foot as'determined by the foot itself or as indicated, for example, by a shoe appropriate for such foot. The current of the electro-rnagnet 28 is then turned partly on, .aslindicated tat 34in :Fig. 1, to

' set; up a: magnetic field between the side walls I2 and M which will have lines of force passing through the space occupied by the mass of balls 90; This magneticfield will magnetize the iron balls'to an extent sufficient to cause them to ad here somewhat to each other but still to be displaceable under pressure. The person then bears his weight up on his foot which causes the foot to sink further intothe balls until the foot is embedded up to about the tops of :the toes. The

' current of the electro-magnet is then turned on full, as indicated in Fig. (l, to cause the density of the magnetic field between the side walls l2 and M to become greatly increased, therebymagnetizing the balls to such an extent that they become a'substantially rigid mass which cannot be'displaced by'further' pressure asilong as the current remains on. The 'foot is then withdrawn from the mass of balls to leave an impression 93 therein which'corresponds exactly to the shape of the foot 92. andwhich is permanent as long as the magnetic field is'maintained.

A thin sheet 96. of. limp stretchable material such .asrubber is now laid in the impression 93, therebylining the impression and covering the small openings between the balls. Plastic mag terial 95, such as plaster of Paris in a liquid or semi-liquid condition, is poured into the impression to coverthe' rubber Iiningsheet- -M and to is now allowed-to. set until itis in semi-solid condition atwhich time a small circular level 96,

fill the impression substantially to the top. During this step of the method thecurrent of the electro-magnet 20 remains fullyon to maintain the field at its maximum density-so that the balls will not become displaced and the impression damaged or destroyed. The plastic material 95 commonly referred to as a spirit level, is pressed into the semi-so=lid material'at about the center ample, for use in'the manufacture of orthopedic V Fig-6 shows the. completed cast 98 after of the heel endof .the impression. The level is moved about until it indicates that its lower surface is exactly horizontal and the plastic material is-then allowed to harden to form the completed cast 98. (Fig. 5).

After the cast has hardened the current is turned on by moving the rheostattd around to tlrie'clos-ed position indicated in Fig. 15, thereby destroying the magnetic field and permitting the "balls to'b'ecor'ne looseand readily movableagain.

shoes. 7 the rubber sheet and the .spirit level have been removed. A circular impression I00 formed by the spirit level will be seen at the heel end of the cast, the bottom surfaceoi. this impression pedic'shoes'since all measurements taken from forming means whereby the cast can be easily located in exactly "the same position which it occupied in the original mold by placing a level in the impression lot and moving the cast about until the'level indicates that the bottom surface ofthe impression is exactly horizontal; This facilitates the use of the cast in' obtaining measurements for use in the manufacture of orthothe cast will. not-only be accurate measurements of the'foot from which the cast was'made butwill also lie-measurements of the foot whenit is located in a natural position and is upporting the weight of the body, the latter condition being essential in orthopedic shoe work. V

Havingthus described the invention what I claim as new and desire to secure by Letters Patent of the United States is .1. Apparatus comprising a container mobile magnetizable material carried thereby and adapt-' 2. An apparatus for reproducing articles comprising a container having magnetizable walls, magnetizable material in the container, said mae terial being readily displaceable to receive an impression of 'an'article to be reproduced, and'a magnet for setting up a magnetic field between the walls of. the container and thereby. rendering said material indisplaceable to hold said impres sion.

3. An apparatus for reproducing articles comprising a container, magnetizable granulated material carried by the container, said material ,being-mobileto form an impression of an article pressed therein, and an electro-magnet for rendering said material rigid to hold the impression.

4. An apparatus for reproducing articles .com-

prising a container, a mass of loose spherical particles of magnetizable material carried by port and a molding medium in which an impression 'of' an article may be made by pressing the'article into said particles and maintaining the pressure, and an electro-magnet for magnetizing the particles while the article is being pressed therein, thereby holding the .particles rigid. to retain the impression after the article is remcvedtherefrom;

.5. An apparatus for reproducing articles'comprising a container, a massof'small iron balls carried thereby, said balls being arranged loosely in the container so that they are relatively movable and may be molded to conform closely to the shape of an article pressed against them, and an electr'o-magnet for magnetizing the balls and causing them to become rigid so that an impression formed therein will be retained after the article has been removed.

.6. An apparatus of the class described hay-- ing, in combination, a container-having opposite side walls of magnetizable material, a support in said container of non-magnetizable mate rial, amagnet the ends of the opposite poles of which engage the side walls of the container, thereby causing the magneticflux to be-extended beyond said poles and into said sidewalls, and a mass of loose particles of magnetizab'le material resting on the support and engaging said and engaging said sidewalls thereby .forming a closed magnetic circuit through'the container.

8. An apparatus for making casts of articles comprisinga rectangular frame having side walls of magnetizable material, a non-magnetizable support mounted in said frame, magnetizable material carried by said support, said material being originally in a mobile condition so that an impression of an article may be formed therein by pressing thev article into said material, and an electro-magnet engaging said side walls and extending the field of the magnet into the space occupied by said magnetizable material, thereby magnetizing said material and causing it to become rigid, so that the impression will be retained when the article is removed, thus permitting the impression to be utilized for producing a cast of the article.

9. An apparatus for making casts of articles comprising a hollow rectangular frame having relatively thick side walls of iron and thin end walls of brass, an aluminum support mounted in said frame, a plurality of small iron balls on said support, said balls forming a mobile mass of magnetic material that can be readily molded by pressure into various shapes, and an electromagnet constructed and arranged to engage the iron Walls of the frame and to set up a magnetic field which will be of greatest density in the space occupied by the balls, thereby magnetizing said balls sufficiently to cause them to become rigidly fixed in whatever positions they have been molded.

10. In an apparatus for making cast reproductions of objects, a container, mobile magnetizable material in the container and adapted to form an impression of afoot pressed therein under the weight of the body, means for balancing the foot in the position it is to assume in a shoe, and a magnet for rendering said mobile material immobile to retain the impression formed therein.

11. In an apparatus for making cast reproductions of objects, a container, an adjustable support in the container, mobile magnetizable material resting on the support and adapted to form an impression of a foot which is supporting the weight of the body, means for adjusting the support to balance the foot in accordance with the position it will assume in av shoe appropriate for said foot, and an electro-magnet for magnetizing said mobile material and rendering it rigid to hold the impression formed therein.

12. That improvement in methods of making casts of the extremities of human limbs which consists in placing the extremity of a limb in a mass of loose magnetizable particles which conform readily to the shape of said extremity, thereby producing an impression, magnetizing said particles to lock them in position and thus retain the impression, removing the extremity of the limb from the impression while the particles are still locked in position by magnetization, and utilizing the impression to form a cast of said extremity without demagnetizing the particles.

13. That improvement in methods of making casts of feet which consists in providing a support the supporting surface of which conforms to the longitudinal contour of a. foot in the position it assumes in a shoe, said support having mobile magnetizable material thereon, pressing the foot into said material under the weight of the 'body, thereby forming an impression of the foot in the position it assumes in a shoe, rendering said material rigid by magnetization to hold the impression, removing the foot from the .impression without demagnetizing the material, and using the impression as a mold to produce a cast of the foot while the material is still held rigid b-y magnetization.

14. An apparatus for producing a cast of a foot comprising a rectangular container having two opposite sides of magnetizable materialand its other two sides of non-magnetizable material, means in the container for sup-porting a foot, said means being adjustable heightwise of the container to accommodate different shaped feet, means for adjusting the supporting means, magnetizable smooth-sided particles resting loosely on said supporting means and capable of forming an impression of the foot when displaced thereby, and an electromagnet for engaging the magnetizable sides of the container with its opposite magnetic poles and thereby extending the field of the magnet undiminished in strength into the space occupied by the magnetizable particles to render said particles immovable after an impression of the foot has been made therein.

15. An apparatus for producing a cast of a foot comprising an elongated metal container having side walls of iron and end walls of brass, an ad justable support mounted in said container, said support being made up of several sections so that the upper surface, thereof can be made to con- ,form substantially to the longitudinal contour of the bottom surface of a foot, means for adjusting said support, a mass of small iron particles mounted on the support, said particles being arranged loosely thereon to provide a mobile substance in which an impression of the foot may be made by pressing it .against said particles, an electro-magnet for controlling the mobility of the mass of iron particles, said electro-magnet engaging the side walls of the container and creating a magnetic field in the space occupied by the particles which magnetizes the particles when a current is passed through the electromagnet, and means for controlling the current to .varythe strength of the electro-magnet.

16. An apparatus for producing a cast of a foot comprising a hollow oblong container having side Walls of iron and end walls of brass, a support mounted in said container, said support being made of aluminum and being arranged in relatively adjustable sections so that its upper surface can be made to conform substantially to the longitudinal contour of the bottom of the 'foot operated upon, single means for adjusting the sections of the support relatively to each other, a

mass of small iron balls resting loosely on said support, said balls serving as a support for the foot and as a molding medium in which an impression of the foot can be made bypressing the foot against the balls and maintaining such pressure, an electro-magnet for engaging the side --sion of an article in magnetizable material which is in a mobile condition, rendering the material immobile by magnetization while the article is still resting therein, removing the article from the magnetized material, and using the impression thus formed as a mold from which to produce a cast of the article.

) '18. That improvement in methods of reproducing articles which consists in making an impression of an article magnetizable granulated 'material which is originally in a mobile condition, magnetizing said materialfafter the impression is made sothat the material will become rigid and thus permit removal of the article without disturbing the impression, and utilizing the impres- 'sio-n as amold from which to make a plastercast '10 cast of the article. 19. That improvement in methods of reproducing articles which consists in making an impres- V "castswhich consists in making an impression of V a yield'able object in mobile material consisting of a massof loose magnetizable particles, render- "ing the mass of particles immobile by magnetizaition, therebyrmaintaining the impression formed therein, and using the impression as a temporary mold to produce a cast of said object.

21. That improvement in'methods of making replicas of articles whichconsists' in making an impression of an article in a mobile mass of mag- ;netizable balls,-said balls being small enough in' diameter to'form an accurate impression, mag- "netizing said balls and thereby transforming the "mobil mass into a rigid mass to retain said impression, and using the impression thus formed as a mold with which to produce a replica of the article, p t V V 22. That improvement in methods of making casts which consists in' obtaining an impression of an article by pressing it into a mobile mass of small iron balls, magnetizing said balls to transform the mobi le mass into a rigid mass and therey; retain said impressiom-lining the impression 'with a thin sheet of stretchable material, filling the'lined impression with plastic material, and "permitting theplastic material to set, while the balls are still magnetized, thereby producing a cast of the article. 1 V '23.'That improvement in methods of 'making casts of feet'which' consists in pressing a foot into mobile material comprising a mass of small iron balls, magnetizing the balls to' cause them to adhere closely to each other and thus to form a rigid mass, removing the foot from the balls and thereby leaving an impression of the foot formed therein, said impression being held intact by the magnetized condition of the balls, lining the impression with a thin sheet of limp stretchable.

24. That improvement in methods of making casts of feet which consists in adjusting a sec' tion al supporting plate until its upper surface conforms substantially to the longitudinal contour of the bottom surface of a particular foot,

said plate being mounted within a container and having magnetizable mobile material resting thereon, placing the foot in the mobile material and bearing the weight of thebody thereon until an impression .of the foot is formed in said mobile material, magnetizing said material with an electromagnet to render the material immobile so that the impression will be, preserved when the foot is removed therefrom, removing the foot and lining the impression with a thin sheet of limp stretchable material, pouring plastic material in liquid form into the lined impression, and allowing the plastic material to harden Whilemaintaining the field of the electromagnet' at full a strength, thereby producing a plaster cast of the foot.

25. That improvement in methods of reproducing articles which comprises creating a relatively weak magnetic fieldin the spaceoccupied by a mass of small iron balls resting loosely on a sup- "porting plate and being readily displ'aceable by pressure while adhering closely together in the absence of such pressure, pressing an article to be.

impression thus formed to' produce'a plaster cast of the article, and eliminating the magnetic field entirely from the space occupied by the balls after the cast has hardened thereby causing the balls to become displaceable again to permit removal 0 the cast without injury thereto.

26. The combination with a container, a mobile magnetizable material carried thereby and adapted to receive an impression of an article engaging it under pressure, and a magnet for thereafter rendering said material sufficiently immobile to sustain a substantial pressure.

27. The combination with a container, of mo bile magnetizable'material carried thereby and adapted to conform to the shape of an object en- 1 gaging it under pressure, and a magnet for rendering said material sufliciently immobile to support the object under pressure after the material has conformed to the shape thereof.

28. The combination with a container and mobile magnetizable material in the container adapt.- ed to be displaced under pressure to conform to the shape of an object pressed against it, of a magnet arranged to render said material immobile after it has conformed to the shape of the object, thereby rendering said material capable of supporting said object without further displace-" ment under further pressure. p 7 29. The combination with a container of aplurality of loose particles of magneti'z'ablematerial carried thereby and adjustable to accommodate themselves to the contour of an, object under pressuraand means for magnetizing said particles to cause them to-adhere toone another and thereby to resist displacement from adjusted positions.

CLIFFORD K. MACDONALD. 

